The discussion below about piston weight made me curious enough to weigh some. A std bore cast iron R.A. Lister piston with pin and ring package weighed 9 lbs, 9.2 oz , an India aluminum piston with same components came in at 4 lbs 7.6 oz and an India iron piston weighed 9 lbs, 5.8 oz. You KG types will have to do your own conversion but by any system the iron piston weighs in over double it's aluminum counter part. Somebody a lot smarter than me could do the math for the inertia loads but your engine is starting and stopping that piston 20 times per second @600 RPM. The extra inertia involved at 850 RPM concerned R.A. Lister enough to lighten the pistons for the 8/1 and at the same time upgrade the big end bearing materials. In its favor the CS has a very long rod vs the stroke and the resulting rod ratio reduces the forces at each end of the stroke.
I certainly cannot argue with the success reported previously with higher speeds and iron pistons but I also have to think that Lister didn't change the piston material on a whim? Thus when iron piston engines leave my little enterprise the owners are cautioned to keep them under 650 RPM.